Mid-infrared antennas(MIRAs)support highly-efficient optical resonance in the infrared,enabling multiple applications,such as surface-enhanced infrared absorption(SEIRA)spectroscopy and ultrasensitive mid-infrared det...Mid-infrared antennas(MIRAs)support highly-efficient optical resonance in the infrared,enabling multiple applications,such as surface-enhanced infrared absorption(SEIRA)spectroscopy and ultrasensitive mid-infrared detection.However,most MIRAs such as dipolar-antenna structures support only narrow-band dipolar-mode resonances while high-order modes are usually too weak to be observed,severely limiting other useful applications that broadband resonances make possible.In this study,we report a multiscale nanobridged rhombic antenna(NBRA)that supports two dominant reson-ances in the MIR,including a charge-transfer plasmon(CTP)band and a bridged dipolar plasmon(BDP)band which looks like a quadruple resonance.These assignments are evidenced by scattering-type scanning near-field optical micro-scopy(s-SNOM)imaging and electromagnetic simulations.The high-order mode only occurs with nanometer-sized bridge(nanobridge)linked to the one end of the rhombic arm which mainly acts as the inductance and the resistance by the circuit analysis.Moreover,the main hotspots associated with the two resonant bands are spatially superimposed,en-abling boosting up the local field for both bands by multiscale coupling.With large field enhancements,multiband detec-tion with high sensitivity to a monolayer of molecules is achieved when using SEIRA.Our work provides a new strategy possible to activate high-order modes for designing multiband MIRAs with both nanobridges and nanogaps for such MIR applications as multiband SEIRAs,IR detectors,and beam-shaping of quantum cascade lasers in the future.展开更多
Raman and infrared(IR)spectroscopy are powerful analytical techniques,but have intrinsically low detection sensitivity.There have been three major steps(i)to advance the optical system of the light excitation,collecti...Raman and infrared(IR)spectroscopy are powerful analytical techniques,but have intrinsically low detection sensitivity.There have been three major steps(i)to advance the optical system of the light excitation,collection,and detection since 1920s,(ii)to utilize nanostructure-based surface-enhanced Raman scattering(SERS)and surface-enhanced infrared absorption(SEIRA)since 1990s,and(iii)to rationally couple(i)and(ii)for maximizing the total detection sensitivity since 2010s.After surveying the history of SERS and SEIRA,we outline the principle of plasmonics and the different mechanisms of SERS and SEIRA.We describe various interactions of light with nano/microstructures,localized surface plasmon,surface plasmon polariton,and lightning-rod effect.Their coupling effects can significantly increase the surface sensitivity by designing nanoparticle–nanoparticle and nanoparticle–substrate configuration.As the nano/microstructures have specific optical near-field and far-field behaviors,we focus on how to systematically design the macro-optical systems to maximize the excitation efficiency and detection sensitivity.We enumerate the key optical designs in particular ATR-based operation modes of directional excitation and emission from visible to IR spectral region.We also present some latest advancements on scanning-probe microscopy-based nanoscale spectroscopy.Finally,prospects and further developments of this field are given with emphasis on emerging techniques and methodologies.展开更多
Organic–inorganic halide perovskites are emerging materials for photovoltaic applications with certified power conversion efficiencies(PCEs)over 25%.Generally,the microstructures of the perovskite materials are criti...Organic–inorganic halide perovskites are emerging materials for photovoltaic applications with certified power conversion efficiencies(PCEs)over 25%.Generally,the microstructures of the perovskite materials are critical to the performances of PCEs.However,the role of the nanometer-sized grain boundaries(GBs)that universally existing in polycrystalline perovskite films could be benign or detrimental to solar cell performance,still remains controversial.Thus,nanometer-resolved quantification of charge carrier distribution to elucidate the role of GBs is highly desirable.Here,we employ correlative infrared-spectroscopic nanoimaging by the scattering-type scanning near-field optical microscopy with 20 nm spatial resolution and Kelvin probe force microscopy to quantify the density of electrons accumulated at the GBs in perovskite polycrystalline thin films.It is found that the electron accumulations are enhanced at the GBs and the electron density is increased from 6×10^(19) cm^(−3 )in the dark to 8×10^(19) cm^(−3 ) under 10 min illumination with 532 nm light.Our results reveal that the electron accumulations are enhanced at the GBs especially under light illumination,featuring downward band bending toward the GBs,which would assist in electron-hole separation and thus be benign to the solar cell performance.展开更多
Two-dimensional metal-organic layers(MOLs)from alternatively connected benzene-tribenzoate ligands and Zr6(μ3-O)_(4)(μ3-OH)_(4) or Hf6(μ3-O)_(4)(μ3-OH)_(4) secondary building units can be prepared in gram scale vi...Two-dimensional metal-organic layers(MOLs)from alternatively connected benzene-tribenzoate ligands and Zr6(μ3-O)_(4)(μ3-OH)_(4) or Hf6(μ3-O)_(4)(μ3-OH)_(4) secondary building units can be prepared in gram scale via solvothermal synthesis.However,the reason why the monolayers did not pack to form thick crystals is unknown.Here we investigated the surface structure of the MOLs by a combination of sum-frequency generation spectroscopy,nanoscale infrared microscopy,atomic force microscopy,aberration-corrected transmission electron microscopy,and compositional analysis.We found a partial coverage of the monolayer surface by dangling tricarboxylate ligands,which prevent packing of the monolayers.This finding illustrates low-density surface modification as a strategy to prepare new two-dimensional materials with a high percentage of exposed surface.展开更多
文摘Mid-infrared antennas(MIRAs)support highly-efficient optical resonance in the infrared,enabling multiple applications,such as surface-enhanced infrared absorption(SEIRA)spectroscopy and ultrasensitive mid-infrared detection.However,most MIRAs such as dipolar-antenna structures support only narrow-band dipolar-mode resonances while high-order modes are usually too weak to be observed,severely limiting other useful applications that broadband resonances make possible.In this study,we report a multiscale nanobridged rhombic antenna(NBRA)that supports two dominant reson-ances in the MIR,including a charge-transfer plasmon(CTP)band and a bridged dipolar plasmon(BDP)band which looks like a quadruple resonance.These assignments are evidenced by scattering-type scanning near-field optical micro-scopy(s-SNOM)imaging and electromagnetic simulations.The high-order mode only occurs with nanometer-sized bridge(nanobridge)linked to the one end of the rhombic arm which mainly acts as the inductance and the resistance by the circuit analysis.Moreover,the main hotspots associated with the two resonant bands are spatially superimposed,en-abling boosting up the local field for both bands by multiscale coupling.With large field enhancements,multiband detec-tion with high sensitivity to a monolayer of molecules is achieved when using SEIRA.Our work provides a new strategy possible to activate high-order modes for designing multiband MIRAs with both nanobridges and nanogaps for such MIR applications as multiband SEIRAs,IR detectors,and beam-shaping of quantum cascade lasers in the future.
基金The authors acknowledge financial support from the National Natural Science Foundation of China(21727807,21904112,91950121,and 21872115).
文摘Raman and infrared(IR)spectroscopy are powerful analytical techniques,but have intrinsically low detection sensitivity.There have been three major steps(i)to advance the optical system of the light excitation,collection,and detection since 1920s,(ii)to utilize nanostructure-based surface-enhanced Raman scattering(SERS)and surface-enhanced infrared absorption(SEIRA)since 1990s,and(iii)to rationally couple(i)and(ii)for maximizing the total detection sensitivity since 2010s.After surveying the history of SERS and SEIRA,we outline the principle of plasmonics and the different mechanisms of SERS and SEIRA.We describe various interactions of light with nano/microstructures,localized surface plasmon,surface plasmon polariton,and lightning-rod effect.Their coupling effects can significantly increase the surface sensitivity by designing nanoparticle–nanoparticle and nanoparticle–substrate configuration.As the nano/microstructures have specific optical near-field and far-field behaviors,we focus on how to systematically design the macro-optical systems to maximize the excitation efficiency and detection sensitivity.We enumerate the key optical designs in particular ATR-based operation modes of directional excitation and emission from visible to IR spectral region.We also present some latest advancements on scanning-probe microscopy-based nanoscale spectroscopy.Finally,prospects and further developments of this field are given with emphasis on emerging techniques and methodologies.
基金The authors sincerely thank professor Thomas Taubner and Dr.Martin Lewin for discussions on the calculation with the finite dipole model.This work was financially supported by NSFC(Grant 21727807,21872115,21902135)MOST(Grant 2016YFA0200703)and the Project funded by China Postdoctoral Science Foundation(Grant 2019M652251).
文摘Organic–inorganic halide perovskites are emerging materials for photovoltaic applications with certified power conversion efficiencies(PCEs)over 25%.Generally,the microstructures of the perovskite materials are critical to the performances of PCEs.However,the role of the nanometer-sized grain boundaries(GBs)that universally existing in polycrystalline perovskite films could be benign or detrimental to solar cell performance,still remains controversial.Thus,nanometer-resolved quantification of charge carrier distribution to elucidate the role of GBs is highly desirable.Here,we employ correlative infrared-spectroscopic nanoimaging by the scattering-type scanning near-field optical microscopy with 20 nm spatial resolution and Kelvin probe force microscopy to quantify the density of electrons accumulated at the GBs in perovskite polycrystalline thin films.It is found that the electron accumulations are enhanced at the GBs and the electron density is increased from 6×10^(19) cm^(−3 )in the dark to 8×10^(19) cm^(−3 ) under 10 min illumination with 532 nm light.Our results reveal that the electron accumulations are enhanced at the GBs especially under light illumination,featuring downward band bending toward the GBs,which would assist in electron-hole separation and thus be benign to the solar cell performance.
基金support from the Ministry of Science and Technology of China(No.2016YFA0200702)the National Natural Science Foundation of China(No.21671162 and No.21721001)the XMU Training Program of Innovation and Entrepreneurship for Undergraduates and NFFTBS(No.J1310024).
文摘Two-dimensional metal-organic layers(MOLs)from alternatively connected benzene-tribenzoate ligands and Zr6(μ3-O)_(4)(μ3-OH)_(4) or Hf6(μ3-O)_(4)(μ3-OH)_(4) secondary building units can be prepared in gram scale via solvothermal synthesis.However,the reason why the monolayers did not pack to form thick crystals is unknown.Here we investigated the surface structure of the MOLs by a combination of sum-frequency generation spectroscopy,nanoscale infrared microscopy,atomic force microscopy,aberration-corrected transmission electron microscopy,and compositional analysis.We found a partial coverage of the monolayer surface by dangling tricarboxylate ligands,which prevent packing of the monolayers.This finding illustrates low-density surface modification as a strategy to prepare new two-dimensional materials with a high percentage of exposed surface.
